One of the objectives in elevator development work is to achieve efficient and economical utilization of building space. In recent years, this development work has produced various elevator solutions without machine room, among other things. Good examples of elevators without machine room are disclosed in specifications EP 0 631 967 (A1) and EP 0 631 968. The elevators described in these specifications are fairly efficient in respect of space utilization as they have made it possible to eliminate the space required by the elevator machine room in the building without a need to enlarge the elevator shaft. In the elevators disclosed in these specifications, the machine is compact at least in one direction, but in other directions it may have much larger dimensions than a conventional elevator machine.
In these basically good elevator solutions, the space required by the hoisting machine limits the freedom of choice in elevator lay-out solutions. Space is needed for the arrangements required for the passage of the hoisting ropes. It is difficult to reduce the space required by the elevator car itself on its track and likewise the space required by the counterweight, at least at a reasonable cost and without impairing elevator performance and operational quality. In a traction sheave elevator without machine room, mounting the hoisting machine in the elevator shaft is often difficult, especially in a solution with machine above, because the hoisting machine is a sizeable body of considerable weight. Especially in the case of larger loads, speeds and/or hoisting heights, the size and weight of the machine are a problem regarding installation, even so much so that the required machine size and weight have in practice limited the sphere of application of the concept of elevator without machine room or at least retarded the introduction of said concept in larger elevators. In modernization of elevators, the space available in the elevator shaft often limits the area of application of the concept of elevator without machine room. In many cases, especially when hydraulic elevators are to be modernized or replaced, it is not practical to apply the concept of roped elevator without machine room due to insufficient space in the shaft, especially in a case where the hydraulic elevator solution to be modernized/replaced has no counterweight. A disadvantage with elevators provided with a counterweight is the cost of the counterweight and the space it requires in the shaft. Drum elevators, which are nowadays rarely used, have the drawbacks of heavy and complex hoisting machines with a high power/torque requirement. Prior-art elevator solutions without counterweight are exotic, and no adequate solutions are known. Before, it has not been technically or economically reasonable to make elevators without a counterweight. One solution of this type is disclosed in specification WO9806655. A recent elevator solution without counterweight presents a viable solution. In prior-art elevator solutions without counterweight, the tensioning of the hoisting rope is implemented using a weight or spring, and this is not an attractive approach to implementing the tensioning of the hoisting rope. Another problem with elevator solutions without counterweight, when long ropes are used e.g. due to a large hoisting height or a large rope length required by high suspension ratios, is the compensation of the elongation of the ropes and the fact that, due to rope elongation, the friction between the traction sheave and the hoisting ropes is insufficient for the operation of the elevator. In a hydraulic elevator, especially a hydraulic elevator with lifting force applied from below, the shaft efficiency, in other words the ratio of the cross-sectional shaft area occupied by the elevator car to the total cross-sectional area of the elevator shaft, is fairly high. This has traditionally been a significant factor contributing towards the choice of a hydraulic elevator as the elevator solution for a building. On the other hand, hydraulic elevators have many drawbacks associated with their lifting mechanism and oil consumption. Hydraulic elevators consume plenty of energy, possible oil leakages from the elevator equipment is an environmental risk, the required periodic oil changes constitute a large cost item, even an elevator installation in good repair produces unpleasant smell as small amounts of oil escape into the elevator shaft or machine room and from there further into other parts of the building and into the environment and so on. Because of the shaft efficiency of the hydraulic elevator, its modernization by replacement with another type of elevator that would obviate the drawbacks of a hydraulic elevator while necessarily involving the use of a smaller elevator car is not an attractive solution to the owner of the elevator. Also, the small machine spaces of hydraulic elevators, which may be located at a large distance from the elevator shaft, make it difficult to change the elevator type.
There are a very large number of traction sheave elevators installed and in use. Such traction sheave elevators were built in their time in accordance with the users' needs as conceived at the time and the intended uses of the buildings in question. Afterwards, both users' needs and the uses of the buildings have changed in many cases, and an old traction sheave elevator may have proved to be insufficient in respect of car size or otherwise. For example, older and relatively small elevators are not necessarily suited for the transportation of prams or wheelchairs. On the other hand, in older buildings which have been converted from residential use for office or other uses, a smaller elevator installed in its time is no longer sufficient in respect of capacity. As is known, enlarging such a traction sheave elevator is practically impossible because the elevator car and the counterweight already take up the cross-sectional area of the elevator shaft and there is no reasonable way of enlarging the car.